Creating mosquito-free outdoor spaces using transfluthrin-treated chairs and ribbons

Residents of malaria-endemic communities spend several hours outdoors performing different activities such as cooking, story-telling or eating; thereby exposing themselves to potentially-infectious mosquitoes. This compromises indoor interventions, notably longlasting insecticide-treated nets (LLINs) and indoor residual spraying (IRS). This study characterized common peri-domestic spaces in rural south-eastern Tanzania, and assessed protective efficacies of transluthrin-treated chairs and hessian ribbons against mosquitoes. Two hundred households were surveyed, and their most-used peri-domestic spaces physically characterized. Protective efficacies of these two prototyped interventions were tested outdoor in 28 households in dry and wet seasons, using volunteer-occupied exposure-free double net traps. Center for Diseases Control and Prevention miniature light traps (CDC-LT) were used to estimate host-seeking mosquito densities within outdoor kitchens. Field-collected Anopheles arabiensis and Anopheles funestus mosquitoes were exposed underneath the chairs to estimate 24h-mortality. Approximately half (52%) of houses had verandas. Aside from these verandas, most houses also had peri-domestic spaces where residents stayed most times (67% of houses with verandas and 94% of non-veranda houses). Transfluthrin-treated chairs reduced outdoor-biting An. arabiensis densities by 70-85 % while transfluthrin-treated hessian ribbons caused 77-81% reduction in the general peri-domestic area. Field-collected An. arabiensis (99.4%) and An. funestus (100%) exposed under transfluthrin-treated chairs died. Most houses had actively-used peri-domestic spaces where exposure to mosquitoes occurred. The transfluthrin-treated chairs and ribbons reduced outdoor-biting malaria vectors in these peri-domestic spaces, and also elicited significant mortality among pyrethroid-resistant fieldcaught malaria vectors. These two new prototypes, if developed further, may constitute new options for complementing LLINs and IRS with outdoor protection against malaria and other mosquito-borne pathogens in areas where peri-domestic human activities are common.